1. Field of the Invention
This invention relates to the structure of an angle portion that makes up an insertion portion of an endoscope used for medical use, etc.
2. Description of the Related Art
Generally, with an endoscope for medical use, etc., an insertion portion, for insertion into a body cavity, etc., is connected to a body control portion, and a universal cable, which is detachably connected at least to a light source device, is lead out to the body control portion. The insertion portion comprises, in the order from the side connected to the body control portion, a flexible portion, an angle portion, and a distal end hard portion, and the angle portion, which is connected to the front end of the flexible portion, which can be bent in an arbitrary direction in accordance with an insertion path of the insertion portion, is a portion that can be operated to become bent by an angle control section disposed at the body control portion. An endoscopic observation mechanism, comprising an illumination portion and an observation portion, is mounted to the distal end hard portion, and by performing a bending operation of the angle portion, the direction of the distal end hard portion can be controlled to thereby orient the distal end hard portion towards an insertion path or change the endoscopic observation field.
In regard to the structure of the angle portion, an angle portion structure, equipped with a predetermined number of angle rings, is formed by pivotally joining the angle rings to each other in the front/rear direction successively by means of pivoting joint pins. The outer periphery of the angle portion structure is covered with a net, and this net is furthermore covered with an outer sheath layer formed of a flexible member. The interior of the angle portion structure is thus a passage of a cylindrical shape, and various members are inserted into this passage. Members inserted into this passage include a light guide that transmits illumination light and a signal cable that extends from a solid-state image pickup element disposed at the observation portion (an image guide in the case of an optical endoscope), and an operative instrument insertion channel, an air/water feed tube, etc., are also inserted into this passage.
Here, at the rigid front end part, the front end of the operative instrument insertion channel opens to a position near the observation portion. When an affected part, etc., is found while observing the interior of a body cavity by the endoscopic observation mechanism, the operative instrument insertion channel is used to perform a curative procedure, sampling of tissue, or injection of a medical solution, etc., and a forceps or other operative instrument is inserted into the channel with the insertion portion being inserted inside the body cavity. The operative instrument insertion channel extends into the insertion portion from the body control portion and the portions from the body control portion to the portion connected to the distal end hard portion are formed of a flexible tube that can be bent in arbitrary directions.
In order to enable bending of the angle portion, the angle rings in the front/rear direction are connected in a mutually inclinable manner, and pivoting joint portions are pivotally joined at two locations along the circumference of each angle ring that are separated by 180°. With each angle ring, notched portions are formed obliquely in directions of 90° from each pivoting joint portion, and the angle of inclination of angle rings in the front/rear direction is controlled by the angle of the notched portions. The curvature of bending of the angle portion is thus determined by the length dimension of each angle ring and the inclination angle, that is, the notch width of each notched portion. When the angle rings are pivotally joined at the left and right sides, the angle portion can bend as a whole in the upward and downward directions and when pivotal joining at the left and right sides and at the front and rear are repeated in that order, the angle portion can bend as a whole in the four directions of leftward, rightward, upward, and downward.
In order to make the angle portion become bent by remote operation, two to four angle operating wires are extended from a take-up reel that makes up an angle operating device provided in the body control portion, and these angle operating wires are extended in a manner enabling pushing and pulling operations while being positioned in the circumferential direction by wire guides inside the angle portion. When, for example, the angle portion is to be bent in the upward or downward direction, one of the pair of angle operating wires that are positioned at upper and lower positions is pulled and the other is operated so as to be drawn out. The angle portion is provided for performing the operation of directing the distal end hard portion to a desired direction, and in order to enable the change of direction of the endoscopic observation field at the distal end hard portion from the frontward to the rearward direction, the angle of curvature in at least one direction should be no less than 180° and preferably no less than 200°. The length of the angle portion and the shapes of the angle rings, which form the structural body of the angle portion, are set with the maximum angle of curvature as a basis.
The angle portion is operated to become bent inside a narrow body cavity and thus the locus of the movement of the angle portion in a bending operation is preferably made as compact as possible. Meanwhile, since an operative instrument may be inserted into the operative instrument insertion channel even with the angle portion being bent, the radius of curvature in the maximum bent state is preferably as large as possible in order to enable smooth insertion of the operative instrument.
Here, an arrangement, wherein the length dimensions of the angle rings and the positions of the wire guides, provided for positioning the angle operating wires in the circumferential direction, are varied in the axial line direction to control the bending shape of the angle portion, is disclosed, for example, in JP-A-3-218723.
With the above-mentioned related-art, by making the angle rings decrease continuously in length towards the front end side of the angle portion, that is, towards the side of connection to the distal end hard portion, the radius of curvature of bending of the angle portion is made small, and as a result of the angle portion thus being made compact in movement and the locus of movement of the rigid front end part, in the process of performing a bending operation of the angle portion inside a narrow body cavity, being made compact, the rigid front end part is prevented from becoming pressed strongly against the inner walls of the body cavity during this operation, thereby alleviating the pain that is inflicted on a subject and improving the operability of the angle portion.
However, it is required that the ease of insertion of an operative instrument into the operative instrument insertion channel be good even when the angle portion is in a bent state. Though the operative instrument that is inserted into the operative instrument insertion channel may be a flexible member, such as a tube, the operative instrument may instead be a forceps or other considerably rigid object, which has forceps claws and a forceps claw opening/closing mechanism disposed at the front end and thus with which a portion of some length in the axial line direction is a rigid portion. When the angle portion is bent, the operative instrument insertion channel, which is inserted in the interior thereof also becomes bent at substantially the same curvature as the angle portion, and in the maximally bent state, the operative instrument insertion channel will also become bent sharply. Insertion of a forceps or other operative instrument of poor insertion condition in a passage that is sharply bent in this manner accompanies high resistance against insertion and not only is the operability poor but the inner surface of the operative instrument insertion channel may become pressed by the front end portion of the operative instrument and the flexible tube that makes up the operative instrument insertion channel may become deformed or damaged, etc.